I've just looked at the IOMG webpage, which seems to have various conflicting info.
The November 2015 letter says one thing (not officially recognised), the January 2016 leaflet a bit different (consulting with UK authorities) and the main page says consulting finished/resolved.
Makes most sense to contact the details on the letter, which is where it says to go to for queries.
https://www.gov.im/categories/benefits-and-financial-support/social-security-benefits/disabled-parking/